<p>1,スクロール検知<br>
2,各要素とスクロール位置の差を比較<br>
3,条件に一致する要素と対の目次に、<code>active</code>クラスを追加</p>
<p>dartpad<br style="display:none">
<span class="embed-block zenn-embedded zenn-embedded-card"><iframe id="zenn-embedded__6276f9219d0e7" src="https://embed.zenn.studio/card#zenn-embedded__6276f9219d0e7" data-content="https%3A%2F%2Fdartpad.dartlang.org%2F%3Fid%3D193d697b27deff9ca4f8f4982776b645" frameborder="0" scrolling="no" loading="lazy"></iframe></span><a href="https://dartpad.dartlang.org/?id=193d697b27deff9ca4f8f4982776b645" style="display:none" target="_blank" rel="nofollow noopener noreferrer">https://dartpad.dartlang.org/?id=193d697b27deff9ca4f8f4982776b645</a></p>
<p>gist<br style="display:none">
<span class="embed-block zenn-embedded zenn-embedded-card"><iframe id="zenn-embedded__259fc38531426" src="https://embed.zenn.studio/card#zenn-embedded__259fc38531426" data-content="https%3A%2F%2Fgist.github.com%2Fsuinua%2F193d697b27deff9ca4f8f4982776b645" frameborder="0" scrolling="no" loading="lazy"></iframe></span><a href="https://gist.github.com/suinua/193d697b27deff9ca4f8f4982776b645" style="display:none" target="_blank" rel="nofollow noopener noreferrer">https://gist.github.com/suinua/193d697b27deff9ca4f8f4982776b645</a><br style="display:none">
<img src="https://storage.googleapis.com/zenn-user-upload/e3e1f3057a19-20220323.gif" alt loading="lazy" class="md-img"></p>


Dartでスクロールに連動する目次を作る

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